X0306 4 2017-12-31 0 0000357173 OLD SECOND BANCORP INC OSBC 0001673321 Pilmer Donald 37 S. RIVER ST. AURORA IL 60506 0 1 0 0 EVP Old Second Bancorp, Inc.Common Stock 2017-12-31 4 A 0 110 A 2654 I 401(k) plan Old Second Bancorp, Inc. Common Stock 924 I Profit Sharing Plan Old Second Bancorp, Inc. Common Stock 1450 I Spouse's IRA Old Second Bancorp, Inc.Common Stock 44085.054 D These shares are held in spouse's IRA for which Mr. Pilmer is listed as a beneficiary. Of this total, 110 shares were allocated during the fourth quarter 2017 pursuant to the Old Second Bancorp, Inc. Employees Salary and Savings Plan. Information herein was provided by the Plan Trustee as of 12-31-17. Does not apply. /s/ Donald Pilmer 2017-12-31